Logic Masters Deutschland e.V.

Rules:

Normal sudoku rules apply.
Values outside the grid are both skyscraper clues *and* sandwich clues.
Sandwich rules: the values outside the grid are the sum of the digits sandwiched between 1 and 9 in that row or column.
Skyscraper rules: the values outside the grid indicate how many skyscrapers can be seen from that side. Taller skyscrapers hide the view of lower ones.
Example: valid rows for a value of '5' on the left side of the grid include 234795168 and 456812397.
There are no negative constraints.

All comments, ratings and feedback are very welcome and appreciated.

Hope you like :)

Hint:

If you're having trouble getting started try colouring the cells that can't be 1 or 9. You might be surprised how far this can get you.